同學，你好 項目方差=(0.2-0.1)2*0.3? (0.1-0.1)2*0.5? (-0.05-0.1)2*0.2=0.1*0.1*0.3+0.15*0.15*0.2=0.0075 項目標準差=0.0075的平方根=8.66%